Mix test runs locally, but not in Docker container

Questions / Help
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1

Hi,

I’m able to run my test from my terminal, but if I’m not able to run the tests from within a container.

I get this error when I run docker compose up:

test-1 | Compiling 50 files (.ex) test-1 | Generated easy_solutions app test-1 | ** (exit) exited in: GenServer.call(ExUnit.Server, :modules_loaded, :infinity) test-1 | ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started test-1 | (elixir 1.14.0) lib/gen_server.ex:1027: GenServer.call/3 test-1 | (ex_unit 1.14.0) lib/ex_unit.ex:376: ExUnit.run/1 test-1 | (mix 1.14.0) lib/mix/compilers/test.ex:42: Mix.Compilers.Test.require_and_run/4 test-1 | (mix 1.14.0) lib/mix/tasks/test.ex:543: Mix.Tasks.Test.do_run/3 test-1 | (mix 1.14.0) lib/mix/task.ex:421: anonymous fn/3 in Mix.Task.run_task/4 test-1 | (mix 1.14.0) lib/mix/task.ex:475: Mix.Task.run_alias/6 test-1 | (mix 1.14.0) lib/mix/cli.ex:84: Mix.CLI.run_task/2

I have also tried to replace entrypoint with sleep, so that I can do a docker compose exec test /bin/bash into the container. I can confirm that mix compile works, and I get the same error when I run mix test.

Any suggestions to how I can debug this further?

test.Dockerfile

FROM ubuntu:24.04 ENV MIX_ENV=test ENV DOCKER_BUILDKIT=1 USER root RUN apt update RUN apt install -y erlang-dev elixir erlang-xmerl RUN apt install -y curl git RUN useradd -ms /bin/bash appuser RUN mkdir /app RUN chown -R appuser /app USER appuser COPY . /app WORKDIR /app RUN mix local.hex --force RUN mix local.rebar --force # install dependencies COPY mix.exs mix.lock ./ RUN mix deps.get # compile dependencies COPY config ./config/ ENTRYPOINT ["mix", "test"]

docker-compose.yaml

version: "3" services: test: environment: DATABASE_PATH: priv/databases/test.db SECRET_KEY_BASE: "l7sdfjkhj" build: context: . dockerfile: test.Dockerfile volumes: - ./test_result:/app/test_result
2

I have found this to work previously

ARG ELIXIR_VERSION=1.14.5 ARG OTP_VERSION=26.0.2 ARG DEBIAN_VERSION=bullseye-20231009-slim ARG BUILDER_IMAGE="hexpm/elixir:${ELIXIR_VERSION}-erlang-${OTP_VERSION}-debian-${DEBIAN_VERSION}" ARG RUNNER_IMAGE="debian:${DEBIAN_VERSION}" FROM ${BUILDER_IMAGE} as builder # .... SNIP ... FROM ${RUNNER_IMAGE} # .... SNIP ...
3

Thanks for the suggestion, @jarlah!
Following your advice, I used the Dockerfile generated by mix phx.gen.release --docker.
I added this the the bottom of the Dockerfile:

FROM builder as test WORKDIR "/app" ENV MIX_ENV="test" COPY . . # install mix dependencies RUN mix deps.get --only $MIX_ENV CMD ["mix", "test"]

My docker-compose.yaml looks like this:

 version: "3" services: test: environment: DATABASE_PATH: priv/databases/test.db SECRET_KEY_BASE: "l7sdfjkhj" build: context: . dockerfile: Dockerfile

Now I can run my tests in a CI/CD pipeline by simply executing
docker compose up test

1 Like
4

Is there a reason you are not using a pre-built docker image for that?

You can find them on dockerhub and hex.

They have erlang and elixir pre-installed and you can select the specific version you need.

4 Likes
5

Hi @D4no0,

I wasn’t aware of those images.
Thanks for telling me!